Method and means of presenting a planetarium display

ABSTRACT

The provision of a planetarium projector provided with a nearpoint light source for the projection of the star images and including means for mounting, and maintaining, a star projection sphere concentric with the underside of a hemispherical dome within which the projector means is operatively positioned, to provide a highly realistic, accurate reproduction of the heavens as they appear from a given observation point upon the surface of the earth. The planetarium projector means also includes optical projection means for the sun, moon and planets which includes means for eliminating parallax from these projectors due to their somewhat non-concentric placement relative to the projection dome. Still further, the utilization of a point light source provided with means for decreasing the intensity of the lamp toward that portion thereof responsible for the projection of the fixed star images in the equatorial regions of the projection dome provides a unique method of presenting a planetarium display characterized by a high degree of realism in the projected night sky.

v United States'Patent :19]

Clark 1 Jan. 2, 1973 [76] inventor: William T. Clark, P. O. Box 885,

Jackson, Miss. 39505 221 Filed: Feb. 5, 1968 211 Appl.N0.:703,009

[52] US. Cl ..35/42.5

[51] Int. Cl. ..G09b 27/00 [58] Field of Search ..35/42.5, 45, 47

[56] References Cited UNITED STATES PATENTS 1,693,969 12/1928 ,Villigeret a1 ..35/42.5

3,303,582 2/1967 Farquhar ..35/47 1,616,736 2/1927 Bauersfeld ..35/42.5

2,477,027 7/1949 Wenberg ..35/42.5 UX

2,483,216 9/1949 Marshall ..35/42.5

2,632,359 3/1953 Spitz ..35/42.5

2,803,165 8/1957 Sargenti ..35/42.5

2,885,791 5/1959 Gunning ..35/47 UX 3,074,183 1/1963 Frank ..35/42.53,250,024 S/l966 Douthitt et a1.

3,256,619 6/1966 Frank ..35/42.5

Primary Examiner-Jerome Schnall Attorney-Clarence A. OBrien and HarveyB. Jacobson 57 ABSTRACT The provision of a planetarium projectorprovided with a near-point light source for the projection of the starimages and including means for mounting, and maintaining, a starprojection sphere concentric with the underside of a hemispherical domewithin which the projector means is operatively positioned, to provide ahighly realistic, accurate reproduction of the heavens as they appearfrom a given observation point upon the surface of the earth. Theplanetarium projector means also includes optical projection means forthe sun, moon and planets which includes means for eliminating parallaxfrom these projectors due to their somewhat non-concentric placementrelative to the projection dome. Still further,- the utilization of apoint light source provided with means for decreasing the intensity ofthe lamp toward that portion thereof responsible for the projection ofthe fixed star images in the equatorial regions of the projection domepro vides a unique method of presenting a planetarium displaycharacterized by a high degree of realism in the projected night sky.

3 Claims, 10 Drawing Figures PATENTEDmz I975 SHEET 2 0F 5 PATENTEDJANZms 3,707,786

' sum u or s 'Illll ma-" w v William T. Clark- I INVENTOR.

METHOD AND MEANSOF PRESENTING A PLANETARIUM DISPLAY The presentinvention relates toa method of presenting a planetarium'display with apoint light source, pinhole fixed star projection means. Moreparticularly, the present invention relates to the provision of a methodand means for presenting a highly realistic, accurate planetariumdisplay by the utilization of a point light source pin-hole fixed starprojector means wherein the point light source is disposed concentric tothe projection dome.

Planetarium projectors provided heretofore generally incorporate anincandescent light source for the projection of the images of the fixedstars by either I a pin-hole projection or optical light ray condensingprojection techniques or a combination of the two techniques. It is wellappreciated that both projection techniques have inherent shortcomings.First of all, if pin-hole projection techniques are utilized inconjunction with an incandescent light source, images of the starsprojected onto the projection dome are simply enlarged images of thefinite incandescent filament of the light source. Furthermore, toachieve the degree of starbrightness required for the averageplanetarium display, the filament size of the incandescent light sourcemust, of necessity, be increased to the point that the imagesrepresenting the bright stars would be too large inasmuch as theyconsist of images of the necessarily large filament itself. Someplanetarium projector means provided heretofore have compromised in anattempt to overcome the aforementioned inherent disadvantage of therelatively inexpensive incandescent light source pin-point projectionmeans, by utilizing the pinhole means for the less brilliant stars andoptical, lens system, means for the projection of the brighter starsfrom incandescent light sources. Still further, in the more complexplanetarium projectors provided heretofore, the projection of the fixedstars is achieved by optical projection means solely. However, theutilization of optical projection means solelygreatly increases the sizeand cost of the planetarium projector. n the other hand, the attemptshave been made heretofore to utilize are light sources in planetariumprojectors in an attempt to eliminate the necessity of opticalprojection means while overcoming the inherent disadvantages of thepin-hole projection of star images by utilization of a light sourcehaving a finite incandescent filament.

However, such prior art attempts are characterized by extremely complexlight sources which are so expensive to construct, operate and maintainso as to substantially negate any advantages derived from theirutilization.

Still further, on the one hand, highly complex planetarium projectorsprovided heretofore are generally characterized by a high degree ofaccuracy, where on the other hand, theirless complicated counterparts,in an attempt to simplify the construction thereof, has resulted in theintroduction of gross error particularly with regard to the projectedimages of the fixed stars, so as to render planetarium displays producedby such simplified prior art projectors highly unsuitable asastronomical teaching aids whereby they are of little use other than forthe presentation of a merely entertaining show.

It is an object of the present invention to provide an improvedconstruction for a planetarium projector utilizing a pin-hole fixed starprojection technique.

Another object of the present invention is to provide a novel near pointare light source for planetarium projectors.

A further object of the present invention is to provide a novel methodof presenting a planetarium display wherein all stars and nebulae assumetheir correct positions, appearing to be point sources, and wherein therelative brightness of stars, i.e., the diminishing of the brilliance ofthe stars near the horizon, is extremely realistically reproduced.

Still a further object of the present invention is to provide a novelmethod andmeans of representing a highly accurate planetarium displaywhereby a fixed star projector means is concentrically disposed relativeto a projection dome so as to assure that all stars and nebulaeprojected thereby assume their correct positions without any significantinaccuracy due to the off center fixed star projection means utilizedheretofore.

A still further object of the present invention is to provide for theelimination of parallax from planet projectors comprising a portion of aplanet projection means of a planetarium projector.

Still a further object of the present invention is to provide novelmeans for selectively energizing and deenergizing the planet projectorsof a planetarium projector means.

These together with other objects and advantages which will becomesubsequently apparent reside in the details of the method of the presentinvention and the projector and lamp means used therein as more fullyhereinafter describedand claimed, reference being had to theaccompanying drawings forming a part hereof, wherein like numerals referto like parts throughout, and in which:

FIG. 1 is-a perspective view of the planetarium projector means of theinvention operatively positioned within a projection dome, furthershowing the fixedstar projection means of the projector concentricallydisposed relative to the projection dome;

FIG. 2 is a somewhat schematic front elevational view of the planetariumprojector of FIG. 1;

FIG. 3 is a somewhat schematic side elevational viewof the projectormeans, further showing in phantom lines the alternative position ofcertain components of the projector means when adjusting the projectormeans for changes in latitude;

FIG. 4 is an enlarged crosssectional view of the fixed star projector ofthe planetarium projector means with the light source therein shown inelevation;

FIG. 5 is an enlarged fragmentary side elevational view of the opticalprojection means utilized to project the images of the sun, moon andplanets; I

FIG. 6 is an enlarged medial fragmentary cross-sectional view of the arelight source of the fixed-star projector;

I FIG. 7 is a vertical cross-sectional view through one embodiment of asupport ring for the optical planet projectors;

. FIG. 8 is a front elevational view of another embodiment of a planetprojector carrying means;

FIG. 9 is a perspective view of a polygonal, specifically dodecahedral,fixed star projector means; and

H6. is a fragmentary side elevational view of still another planetprojector carrier means.

Briefly, the present invention provides a method and means of presentinga planetarium display of a high degree of realism and accuracy by thenovel placement of a planetarium projector means provided with a novelnear-point light source, consisting of an enclosed concentrated-arc lampproviding a near-point source of light of a dimension generally in theorder of approximately 0.03 inches, or less, to achieve a full range ofprojected star brilliance corresponding to the natural night sky andwherein all of the projected star images appear to be point source,i.e., images of the intensely bright projected arc, differentiated onlyin apparent brightness wherein disks of light or fuzzy, indistinctimages of a projected finite filament are noticeably absent. The starprojector within which the aforementioned concentrated-arc light sourceis contained, is positioned concentrically relative to the projectiondome whereby and wherein the latitude, precession and diurnal axes ofthe fixed-star projector intersect at the near-point concentrated-arclight source. In addition, the planetary projection means of the presentplanetarium projector is provided with an appropriate number ofindividual optical projectors, each utilizing its own incandescent lightsource and optical, i.e., lens system, light ray condensing means, eachprovided with optical projector carrier means readily facilitatingadjustment of each optical projector to compensate for parallaxintroduced by the non-concentric placement of the optical projectorsrelative to the center of the projection dome.

Still further, the invention contemplates a novel method of presenting ahighly realistic planetarium display wherein the relative brilliance ofthe natural appearance of stars in the area of the zenith region, of theprojection dome, as opposed to the somewhat diminished brilliance of thestars in the region of the horizon, is realistically reproduced, whichmethod also includes a simplified means of simulating conditions withinthe planetarium which correspond to the conditions of daylight,twilight, night, dawn, and back to daylight.

Referring now to the drawings and FIG. 1 in particular, a planetariumprojector means 10 is shown operatively positioned within a projectiondome 12 of conventional construction. It will be understood that theprojection dome 12 is merely exemplary and that the planetariumprojector means 10 may be utilized in conjunction with an observatorydome of generally hemispherical configuration characterized by arelatively unobstructed underside. The planetarium projector means 10,as best seen from a simultaneous consideration of FIGS. 1, 2 and 3,basically comprises a fixed-star projector means 14 having a multitudeof pin-holes as at 15 and a planetary projector means 16 carried by aplanetarium projector support means 18 rigidly secured to a controlconsole and support pylon indicated generally at 20. As will be seenbest from FIG. 1, and particularly the phantom line radii shown therein,the fixed-star projector means 14, and more specifically the near-pointlight source therein, is positioned concentric to the projection dome12, i.e., at the intersection of the radii. Which radii are indicatedgenerally at 22.

As seen best from a simultaneous consideration of FIGS. 2, 3 and 4 thefixed-star projector means 14 is adapted for precise rotation on itslatitude axis 24, precession axis 26 and diurnal axis 28 which axesintersect at a point indicated generally at 30 within the interior ofthe fixed-star projector means 14, which coincides with the concentratedarc point light source provided therein. Thus, it will be'appreciatedthat as the fixed-star projector means 14 is rotated or oscillated aboutthe aforementioned axes 24, 26 and 28 that the concentrated-arc lightsource coinciding with the spatial point 30 will constantly remainconcentric relative to the intersection of the radii 22.

To accomplish the concentric rotational placement of the fixed-starprojector means 14, which in the exemplary embodiment illustrated inFIGS. 1-4 comprises a hollow sphere 32 the planetarium projector supportmeans 18 includes a pair of bifurcated upstanding bracket members 34provided with shaft journal means 36 adjacent the top thereof withinwhich is rotatably joumalled a yoke means 38 consisting of horizontallydisposed shaft means 40 secured to the arms 42 of the yoke means 38 andjoumalled in the means 36 for rotation of the yoke means about thelatitude axis 24. In FIG. 3 it will be seen that the fixedstar projectormeans 14 and the planetarium projector means 16 are shown in successiverotational positions prescribed about the latitude axis 24.

The journal means 36 will thus be understood to include a manual orpower operated means for selectively positioning the yoke assembly 38about the latitude axis 24. The yoke assembly 38 further includes adiurnal motor housing 44 for supporting a diurnal motion shaft 46 havingits axis of rotation coinciding with the diurnal axis 28. The precessionaxis arm 48 fixed to the diurnal shaft 46 generally normal theretoincludes an outwardly disposed portion 50 which supports a precessionaxis shaft 52 having an axis of rotation coinciding with the precessionaxis 26, which it is understood deviates 23% from the diurnal axis 28 soas to rotate the fixed-star sphere 32 around the precession axis 26 inorder that the planetary projector means 10 can display a complete cycleof approximately 26,000 earth years. Thus, and as best seen in FIG. 4,the fixedstar sphere 32 is fixed to the precession axis shaft 52 and itwill be understood that although not nonnally required an appropriatedrive means, not shown, may be provided to rotate the sphere 32 aboutthe precession axis 26 as the diurnal drive means 44 rotates both thesphere 32 and the planetary projector means 16 about the diurnal axis28. As seen best in FIG. 4, an enclosed concentrated-arc light sourceindicated generally at 60, such as comprising a zirconium arc lamp forexample, is supported in a pendulum light support means 62 including alight support arm 64 fixed relative to the precession axis shaft 52 forrotation therewith, and provided with upstanding support brackets 66within which, in pendulum fashion, is supported a yoke means 68 by meansof pivot means 70. The yoke means 68 further includes an arc lampmounting socket 72 connected to a suitable source of starting andenergizing current for the lamp 60, generally provided in the controlconsole 20. The lamp support yoke 68 further includes weight means 74 toinsure that the lamp remains in a substantially upright position, asillustrated in FIG. 4, or during rotation of the device about thelatitude axis 24, as shown in FIG. 3.

Referring now to FIG. 6 it will be seen that the lamp 60 consists of anenclosed concentrated-arc lamp such as is characterized by a zirconiumcathode 76, projecting upwardly with an aperture 77 at the zenith of aconvex anode shield 78 wherein suitable energization of the lamp 60establishes a brilliant light emitting are between the zirconium element76 and the anode shield 78 thus providing a near-point light sourcewhich when operatively positioned within the device of the presentinvention preferably coincides with the spatial point 30 correspondingto the center of the projection dome within which the device isutilized. The lamp 60 is preferably also provided with a hemisphericalenvelope end portion 80 which coacts with the convex anode shield 78 sothat illuminating light will decrease downwardly along the verticalaxis, running longitudinallythrough the zirconium cathode 76, or zenithof the envelope end portion 80, which illumination decreases downwardlyfrom the zenith in accordance with a cosine curve whereby fixed starimages projected on the horizon of the projection dome 12 are not asbright as those projected at the zenith of the dome 12. In addition, itwill be noted that the zirconium cathode 76 projects upwardly within thethrough aperture 77 at the zenithof the convex anode 78 and wherein theuppermost end of the cathode 76 terminates just short of the uppersurface of the anode 78 and wherein the zenith of the anode shield 78coincides with an equatorial plane through the hemispherical envelopeportion 80 of the lamp 60.

It has been noted that the aforedescribed construction of the arc lamp60 is generally necessary to carry out the objects of the presentinvention.

The fixed-star projector sphere 32 may, for example, comprise a spherehaving a 12-inch radius and may for example have a total of somewhatmore than 1,000 holes drilled therethrough, ranging in size from 0.0520inch to 0.0135, inch for example, to accomplish the pin-point projectionof fixed stars and nebulae corresponding in brilliance to the actualstar brilliance. As seen in FIG. 9, the fixed-star projector means 14need not necessarily include a spherical housing 32 but may generallycomprise any hollow regular geometric form, such as dodecahedron 33illustrated. In addition, although not shown, the present invention alsoencompasses the utilization of dual projectors, i.e., two generallyhemispherical pin-hole projection members, each having an enclosed-arclight source. In this regard, it will be appreciated that the dualprojector concept comprises an improvement over the extremely complexdual star projector means presently utilized in the more 1 complex andcostly planetarium display projection means. Referring once again toFIGS. 2, 3 and 4 with particular regard to the diurnal drive means 44,and the planetary projector means 16, it will be seen that the shaft 86common to all the planetary cages provided for-each of the planetaryprojectors to be described hereinafter. As indicated hereinbefore theplanetary projector means 16 generally rotates about the diurnal axis28. In addition, the planetary cages, comprising the ecliptic projector88, moon projector 90, Mercury projector 92, Venus projector 94, Marsprojector 96, Jupiter projector 98, Saturn projector 100, and sunprojector 102 generally rotates about a planetary projection axis 104having an angle of 23% relative to the diurnal axis 28 and generallyparallel to the axis 26, and wherein the drive shaft 86, comprising theoutput shaft of the planetary drive means 84, provides drive means foreach of the aforementioned projectors by means to be describedhereinafter. In addition, an equator projector 106 preferably comprisesa part of the diurnal drive means 44. From the foregoing, it will beapparent that in the broad sense, that the equator and ecliptic diurnalaxis rotational shaft 46 driven by a motor means, not shown, within thediurnal drive housing 44 includes a downwardly disposed eccentric arm 82which carries the planetary projector means 16 and includes a planetaryprojector drive means 84 including a suitable drive motor, not shown,which drives a drive projectors as well as the moon, sun and planetprojectors are somewhat analogous to those conventionally provided inprior art planetarium projector means. However, as will become apparent,the aforementioned projectors in the device 10 of the present invention,are characterized by novel mounting, drive and parallax eliminationadjustment means.

In this regard, and referring now first to FIG. 5 comprising exemplarydetails of the planetary gear means 108 and earth gear means typical ofthe sun, moon and planet projector cages, somewhat schematically shownin FIGS. 2 and 3, wherein due to scalar limitations only the supportplate for each of the planetary cages is shown. In setting forth theexemplary similarity of the planetary gear meansvl08 itjs not meant toimply that the planetary gear means for each of the planetary projectorsis identical inasmuch as the celestial path and speed of each differs.However, and as will become apparent hereinafter, each of theaforementioned planetary projectors is characterized by analogous novelconstructional features. Although the motions of the planetaryprojectors are quite intricate, extreme accuracy is achieved by drivingthe sun, moon and planetary projectors from the common drive shaft 86.In addition, the gear ratios utilized, for each of the planetary gearmeans 108 is geared to the fourth significant integer. For example, theperiod of the planet Mars is approximately 1.880 earth years; and in theplanetarium projector means 10 illustrated the scale is l .875. Inaddition, as will become apparent hereinafter, the sun, moon, andplanetary projectors each include adjustment means in order to permitthe correction of periodic slight errors that may arise.

Referring now more specifically to the planetary gear means 108 andtheir associated earth gear means 110, to correlate the movement of theprojected sun, moon and planet images relative to the earth, and, theiras- -sociated optical projector means 112, it will be understood thatwith the planetary revolution of the earth being 1 the planetary gearmeans 108 of each of the planetary projectors will comprise a ratiorevolution of 0.4152 for the Mercury projector 92; 1.625 for the Venusprojector 94; 1.875 for the Mars projector 96; 11.82 for the Jupiterprojector 98', and 29.45 for'the Saturn projector 100. Thus, anexemplary gear drive 108 comprises a drive gear 114 carried by and fixedrelative to the planetary drive shaft 86 with a plurality ofappropriately sized idler gears 116 and 118 carried on stub shafts 117and 119 respectively, secured to their respective planetary cagemounting plate 120, drive a planetary gearing output gear 122 having anintegral downwardly depending shaft 124 to which is fixed a planetaryprojector support arm 126 provided with a projector support carriermeans indicated generally at 128 which in addition to be rotated underthe influence of the support arm 126 is also simultaneously rotated in acompound motion by the associated earth gear means 110 and itsassociated guide arm indicated generally at 111. As does the planetarygear means, the earth gear means 110 includes a drive gear 130 carriedby and fixed relative to the planetary drive shaft 86, intermediategears 132 and 134 which ultimately drive the gear 136 to which is fixedthe earth guide arm drive lever 138. It will be understood, of course,that the gear ratio of each of the earth gear means 110 is identical.

Inasmuch as the angular relationship of the orbit of each of the planetsdiffer with respect to each other and the precession axis of the earthor the longitudinal axis of the planetary projector means 16, which aswas discussed hereinabove, are both inclined 23l relative to the diurnalaxis 28. Accordingly, a predetermined inclination of the plane ofrotation of the respective projector support arms 126 is introduced bythe placement of angular shim 140 affixed relative to its contiguousplanetary cage plate member 120 whereby the associated gear 122 rotatesabout its associated stub shaft 123' at an angle which deviates thepredetermined number of degrees from the planetary axis 104. Thus, asseen in FIG. the angular shim members 140 of the two complete planetaryprojector cages shown and the fragmentary projector means shown. are ofvarying thickness and therefore effect varying inclination of theirassociated projector support arms 126.

With further regard to the optical projectors 112 each comprises atubular barrel 113 provided with an incandescent light source 115 and alight condensing lens system 117. As seen best in FIG. 7 intennediatethe ends thereof, the tubular member 113 isprovided with an annular rib119, such as comprising an integral annular ring, O-ring engagedthereabout, etc. The annular rib 119 is received within a projectorcarrier member 121, which as seen in FIG. 5, is pivotally carried as at123 by a yoke 125 carried by its respective projector support arm 126,which carrier member 121 fixedly receives one end of the earth guide arm111 at a point therein corresponding to the intersection of the pivotalaxis 123 and the axis of the securement of the yoke 125 to the member126. Furthermore, parallax elimination means is provided in the carriermember 121 by the provision of a pair of setscrews 123" threadablyreceived in threaded-through apertures in the carrier member 121 so asto adjustably bear against the tubular member 113 at pointslongitudinally spaced from the annular rib 119 whereby by selectivelytightening the setscrews 123" disproportionately the projector 112 maybe selectively disposed at an angle other than normal to the verticalaxis provided by the yoke 125 whereby the position of the sun, moon orplanetary image impinging on the projection dome 12 may be adjusted toeliminate parallax introduced by the non-concentric placement of theplanetary cages with respect to the projection dome 12. Alternatively,although not shown, the parallax elimination means could comprise aninwardly projecting annular ring integral with or carried by the carriermember 121 rather than the tubular member 113.

In addition, the projector carrier means 128, more specifically thecarrier member 121, is preferably provided with an angularly responsiveelectrical switch means, i.e., a mercury switch 129, whereby as itsassociated planetary projector 112 dips below the horizon of theprojection dome 12 the associated incandescent light means 1 15 isdeenergized.

Referring now to FIG. 8 it will be seen that the carrier member 121 ofthe projector carrier means 128 and including the yoke 125 may bereplaced by an analogous projector carrier means 228 provided withoptical projectors 112. Each of the projectors 112 in the carrier means228 is aimed at the same point whereby the images are superimposed. Thisserves a twofold purpose, first in the event of the bum-out of one lampthe other will generally continue to operate, and secondly as theprojectors sweep past the support rods for the plates 120 at least oneof the projected images will not be blocked. Thus, it will be seen thatthe dual projector means 228 includes a carrier 221 yoke 225 carried bythe associated support 126 and pivoted to the carrier member 221 as at223 in a manner analogous to the embodiment 128 whereby'the earth guidearm 111 is fixedly secured to the carrier member 221 at a pointcorresponding to the intersecting axes of the yoke 225 and the pivotalmeans 223. Although not shown, it will be understood that the dualprojector carrier means 228 may also be provided with an inclinationresponsive electric switch analogous to that illustrated with regard tothe embodiment of FIG. 7.

Still further, and now referring to FIG. 10, it will be seen thatanother embodiment of projector 112 support means includes an off-setprojector tube carrier member 321 and wherein in the embodiment shown inconjunction with an alternative construction of the Mercury projector,the primary support of the projector 112 is derived from a support arm311 carried by the last driven gear 336 in the earth gear trainpivotally secured as at 337 to projector carrier mounting block 339which in turn carries a planetary guide arm 339 adjustably received in apost 341 carried by the planetary guide arm 343 which is in tum integralwith the last gear 122 in the planetary gear drive means 108 carried bya planetary projector cage support plate 120. Furthermore, although notmentioned hereinabove, the gears 116 of each of the respective planetarycages is spring-biased into the position shown on its associated stubshaft 117 whereby it may be biased downwardly to disengage it from itsassociated drive gear 114 and driven gear 118 so as to permit adjustmentof the last gear 122 and thus the support arm 126, or conversely the arm343, to facilitate adjustment of the projector 112 to compensate foraccumulative rotational error, and the like which is introduced asdiscussed hereinabove. In addition, and as seen in FIG. 5, the operativeconnection between the first guide am 138 and the first guide rod 111 aswell as the operative connection between the planetary guide arm 339 andits associated post 341 include means whereby the respective rods 111and 339 can be angulated with regard to the respective posts 141 and341, as necessary by virtue of thenon-parallel axes of the rotation ofthe arms 138 relative to the arms 126 or conversely the rotation of thearms 311 relative to the arms 343. Furthermore, it will also beappreciated that the posts 141 and 341 slidably engage their respectiverods 111 and 339 due to the eccentric motion of their respectively arms138 and 343 during planetary movement of their respective projectors112.

While brief mention has been made heretofore -to auxiliary devicesassociated with the basic means, i.e., fixed-star projection, as well assun, moon and planet projection, the planetarium projector means 10 mayfurther include as accessories special effect light means indicatedgenerally at 250, such as associated with the yoke bearing assemblies 38wherein the provision of incandescent light sources 252 in cooperationwith transparent domes 254 permit the simulation of clouds, etc. by theutilization of appropriate light masks thereover or actual non-permanentmarking of the dome 254 with a light opaque substance.

With more specific regard to the method of the present invention, itwill be seen that FIG. 2 shows the planetary and projector means 10 withthe planetary cages 16 in the lowest possible position. Thisconfiguration would be used to project or depict the night skies as seenby an observer from a location at the North Pole of the earth.Therefore, rotation of the means14 and 16 about the diurnal axis 28 bythe diurnal drive means will simulate the diurnal, or daily, apparentmotions of the earth. As further seen in FIG. 2, rotation of themeans l4and 16 by the diurnal drive means 44 does not effect the precessionaldisplacement of the axes "of the means 14 and 16, as shown in phantomlines. Referring now to FIG. 3, where for purposes of simplicity only anadjustment in latitude has been shown, thus no diurnal rotation, it canbe seen that the projection means 14 remains concentric with theprojection dome 12. Thus it will be seen that the brilliant point lightsource provided by the energized lamp 60 shines outwardly through themultitude of pin-holes in I the exemplary sphere 32 to impinge upon theunderside of the projection dome 12 as a corresponding multitude ofpoints of light of brilliance proportionally corresponding to therelative size of the pin-hole associated therewith and whereinregardless of diurnal, precessional or latitude rotation of a sphere 32the light source coinciding with the point 30 will each remainsubstantially uniformly spaced from the dome, i.e., concentrictherewith, thereby providing a high degree of accuracy not possible withrelatively simple planetarium projector means provided heretofore.

Furthermore, and as discussed hereinabove, the provision of an enclosedconcentrated-arc'lamp, as the lamp 60 characterized by the cathode,anode, hemispherical envelope shown, provides a highly realisticplanetarium display wherein the relative apparent construction in thebrightness of stars near the horizon diminishes as in nature. In thisregard, it will be appreciated that in nature this apparent reduction ofthe brilliance of the stars near the horizon is caused by increased airmass toward the horizon of the earth through which an observer views thestars in that region. Considering the air mass toward the zenith of thatportion of the sky being viewed, as one, or unity,the

apparent brightness of two equally brilliant stars would be diminishedby some 36 light diffusing, air masses. Therefore, it will be apparentthat falling off a brilliance of natural stars toward the horizon isextremely close agreement with the cosine function of the light source60, disclosed herein, thereby introducing a degree of realism notgenerally possible with relatively simplified planetarium projectorsprovided heretofore.

Although not discussed heretofore, it will be appreciated that thebrilliance of incandescent light sources in star projector orplanetarium projector means provided heretofore is controlled by arheostat in order to vary the projected star brilliance, or intensity.However, as is well known, an arc lamp, such as the arc lamp disclosedis either on or off, with no variation of brilliance in between. Thus,utilization of an arc lamp as disclosed would compensate for lightscattering air masses, but wherein the stars are basically of the samebrilliance facilitates carrying forth of a highly realistic planetariumdisplay by selectively controlling incandescent lamps'within the dome,such as comprising incandescent elongated lamps 350 placed about theperiphery of the dome 12 as seen in FIG. 1 to change the relativeillumination in the dome 12 whereby the varying of the lights 350 tocorrespond to conditions of daylight, twilight, night, dawn, and back todaylight to cause the stars to appear to be going through the cycle ofinvisibility to full brilliance as the sunsets.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modifications and changes willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact method, construction, and operation shown anddescribed, and accordingly all suitable modifications and equivalentsmay be resorted to falling within the scope of the invention as claimed.

What is claimed as new is as follows:

1. In combination with a generally hemispherical projection dome, aplanetarium projector including a star projector means concentricallydisposed relative to the intersection of the radii of the dome whichcomprises yoke means supporting said star projector means, meanssupporting said yoke means for at least partial rotation about agenerally normally horizontal axis, generally coinciding with anequatorial plane through said dome, a first shaft means carried by saidyoke means, said first shaft means including a first output shaft meanshaving-a rotational axis normal to and intersecting said generallynormally horizontal axis, an eccentric arm means carried by said firstoutput shaft means for rotation therewith generally on a plane normalthereto, a second shaft means carried by said arm means at a point.spaced from said rotational axis thereof and including a second outputshaft means having a rotational axis inclined relative to the rotationalaxis of said first output shaft means a number of degrees approximatingthe inclination of the earth axis, the rotational axis of said secondoutput shaft means intersecting said horizontal rotational axis of theyoke means and the rotational axis of the first output shaft means, saidstar projector means being carried by said second output shaft means forconcentric rotation therewith with the point of intersection of thegenerally normally horizontal rotational axis of the yoke means,

the normal rotational axis of the first output shaft means, and theinclined axis of said second output shaft means coinciding with thepoint of intersection of the radii of said projection dome, and saidstar projector means including light ray generating means mountedtherein and coinciding with the point of intersection of the radii ofthe dome for projecting star images upon said planetarium projectiondome, and planetary projection means carried by said first output shaftmeans for rotation therewith and disposed in generally diametricallyopposed relation to said arm means, said planetary projection meanshaving an inclined longitudinal axis generally parallel to therotational axis of said second output shaft means, said planetaryprojection means including a plurality of planetary projectors eachincluding means rotatably driving them generally about the longitudinalaxis of said planetary projection means and on a plane generally normalthereto.

2. The planetarium projection of claim 1 wherein at least one of saidplurality of planetary projectors includes means for selectivelyinclining said at least one of said plurality of planetary projectorsrelative to said longitudinal axis of said planetary projection means togenerally eliminate parallax of the images projected thereby broughtabout by the generally non-concentric placement of said planetaryprojection means relative to said star projector means.

3. In combination with a generally hemispherical projection dome, aplanetarium projector including a star projector means concentricallydisposed relative to the intersection of the radii of the dome whichcomprises yoke means supporting said star projector means, meanssupporting said yoke means for at least partial rotation about agenerally normally horizontal axis, generally coinciding with anequatorial plane through said dome, a first shaft means carried by saidyoke means, said first shaft means including a first output shaft meanshaving a rotational axis normal to and intersecting said generallynormally horizontal axis, an eccentricfarm means carried by said firstoutput shaft means for rotation therewith generally on a plane normalthereto, a second shaft means carried by said arm means at a pointspaced from said rotational axis thereof and including a second outputshaft means having a rotational axis inclined relative to the rotationalaxis of said first output shaft means a number of degrees approximatingthe inclination of the earth axis, the rotational axis of said secondoutput shaft means intersecting said horizontal rotational axis of theyoke means and the rotational axis of the first output shaft means, saidstar projector means being carried by said second output shaft means forconcentric rotation therewith with the point of intersection of thegenerally normally horizontal rotational axis of the yoke means, thenormal rotational axis of the first output shaft means, and the inclinedaxis of said second output shaft means coinciding with the point ofintersection of the radii of said projection dome, and said starprojector means including light ray generating means mounted therein andcoinciding with the point of intersection of the radii of the dome forprojecting star images upon said planetarium projection dome, said lightray generating means comprising an enclosed concentrated-arc lightsource providing near-point source illumination, said enclosedconcentrated-arc light source including cathodt means, C(illVCX anodemeans and a general y hemisp erical enc osure end portion having anequatorial region disposed on a plane normal to the zenith of said anodeshield, said cathode means being operatively positioned relative to saidanode shield generally at the zenith thereof whereby the light intensityoutput characteristics of said light source diminishes in brilliancefrom the zenith of the generally hemispherical enclosure end portiontoward the equatorial region of said generally hemispherical enclosureend portion thereby providing a reduction of the brilliance of the starsnear the horizon when projecting star images upon said planetariumprojection dome.

1. In combination with a generally hemispherical projection dome, aplanetarium projector including a star projector means concentricallydisposed relative to the intersection of the radii of the dome whichcomprises yoke means supporting said star projector means, meanssupporting said yoke means for at least partial rotation about agenerally normally horizontal axis, generally coinciding with anequatorial plane through said dome, a first shaft means carried by saidyoke means, said first shaft means including a first output shaft meanshaving a rotational axis normal to and intersecting said generallynormally horizontal axis, an eccentric arm means carried by said firstoutput shaft means for rotation therewith generally on a plane normalthereto, a second shaft means carried by said arm means at a pointspaced from said rotational axis thereof and including a second outputshaft means having a rotational axis inclined relative to the rotationalaxis of said first output shaft means a number of degrees approximatingthe inclination of the earth axis, the rotational axis of said secondoutput shaft means intersecting said horizontal rotational axis of theyoke means and the rotational axis of the first output shaft means, saidstar projector means being carried by said second output shaft means forconcentric rotation therewith with the point of intersection of thegenerally normally horizontal rotational axis of the yoke means, thenormal rotational axis of the first output shaft means, and the inclinedaxis of said second output shaft means coinciding with the point ofintersection of the radii of said projection dome, and said starprojector means including light ray generating Means mounted therein andcoinciding with the point of intersection of the radii of the dome forprojecting star images upon said planetarium projection dome, andplanetary projection means carried by said first output shaft means forrotation therewith and disposed in generally diametrically opposedrelation to said arm means, said planetary projection means having aninclined longitudinal axis generally parallel to the rotational axis ofsaid second output shaft means, said planetary projection meansincluding a plurality of planetary projectors each including meansrotatably driving them generally about the longitudinal axis of saidplanetary projection means and on a plane generally normal thereto. 2.The planetarium projection of claim 1 wherein at least one of saidplurality of planetary projectors includes means for selectivelyinclining said at least one of said plurality of planetary projectorsrelative to said longitudinal axis of said planetary projection means togenerally eliminate parallax of the images projected thereby broughtabout by the generally non-concentric placement of said planetaryprojection means relative to said star projector means.
 3. Incombination with a generally hemispherical projection dome, aplanetarium projector including a star projector means concentricallydisposed relative to the intersection of the radii of the dome whichcomprises yoke means supporting said star projector means, meanssupporting said yoke means for at least partial rotation about agenerally normally horizontal axis, generally coinciding with anequatorial plane through said dome, a first shaft means carried by saidyoke means, said first shaft means including a first output shaft meanshaving a rotational axis normal to and intersecting said generallynormally horizontal axis, an eccentric arm means carried by said firstoutput shaft means for rotation therewith generally on a plane normalthereto, a second shaft means carried by said arm means at a pointspaced from said rotational axis thereof and including a second outputshaft means having a rotational axis inclined relative to the rotationalaxis of said first output shaft means a number of degrees approximatingthe inclination of the earth axis, the rotational axis of said secondoutput shaft means intersecting said horizontal rotational axis of theyoke means and the rotational axis of the first output shaft means, saidstar projector means being carried by said second output shaft means forconcentric rotation therewith with the point of intersection of thegenerally normally horizontal rotational axis of the yoke means, thenormal rotational axis of the first output shaft means, and the inclinedaxis of said second output shaft means coinciding with the point ofintersection of the radii of said projection dome, and said starprojector means including light ray generating means mounted therein andcoinciding with the point of intersection of the radii of the dome forprojecting star images upon said planetarium projection dome, said lightray generating means comprising an enclosed concentrated-arc lightsource providing near-point source illumination, said enclosedconcentrated-arc light source including cathode means, convex anodemeans and a generally hemispherical enclosure end portion having anequatorial region disposed on a plane normal to the zenith of said anodeshield, said cathode means being operatively positioned relative to saidanode shield generally at the zenith thereof whereby the light intensityoutput characteristics of said light source diminishes in brilliancefrom the zenith of the generally hemispherical enclosure end portiontoward the equatorial region of said generally hemispherical enclosureend portion thereby providing a reduction of the brilliance of the starsnear the horizon when projecting star images upon said planetariumprojection dome.